Hard as it may be to believe, many people enjoy the challenge of camping in the snow. The special beauty of winter landscapes is worth those sometimes sub-zero mornings.

There are a number of ways to camp in a winter environment, some more comfortable than others. Among the possibilities (most designed for less than 10 participants):

* Mountaineering in the Adirondacks: Learn winter survival skills -- snowshoeing, building ice caves, carrying a backpack in heavy snow. A three-day course near Lake Placid, N.Y. is $150 per person for food, gear and guide. The next trip begins March 5. In April, classes move to Jackson, Wyo. Vermont Voyageur Expeditions, Star Route, Montgomery Center, Vt. 05471, (802) 326-4789.

* Dog-sledding in Canada: Join an Indian guide traveling his trap line in Canada's Northwest Territories. "Camp beneath the Northern Lights," says the outfitter, "and be serenaded by the eerie, lonesome howling of wolves." From three to five days, beginning April 1 and 7; $140 a day per person, including food and gear. Sobek Expeditions, Angels Camp, Calif. 95222, (209) 736-4524.

* Exploring Yellowstone: By snow-cat and cross-country skis, you tour the geyser basins and view the Grand Canyon of the Yellowstone in America's oldest national park. Nights at the canyon in an established tent camp (each tent is equipped with flooring and a propane heater). Two departures weekly, Friday and Tuesday, for two nights from mid-December to mid-March; $210 per person for food, lodging, transportation. Yellowstone Expeditions, Box 865, West Yellowstone, Mont. 59758, (406) 646-9333.

* Ski touring in Colorado: Glide on skis, tent on your back, into the Marroon Bells wilderness area outside Aspen. Five days of lessons (beginners to experienced) in ski touring and winter camping. Departure March 18; $325 per person for food, gear, guide. Range Tours, 1540 S. Holly St., Denver, Colo. 80222, (800) 525-8509.

* Ice-climbing in Wyoming: Here's the chance to try a relatively new winter sport -- climbing frozen waterfalls. Three days of lessons on a moderate ice slope in the Wind River Mountains near Dubois. Outings arranged through March; $150 per person for food, gear, instruction. Jackson Hole Mountain Guides, P.O. Box 547T, Teton Village, Wyo. 83025, (307) 733-4979.

* Hiking in West Virginia: You arrange the date, and the Outdoor School of Herndon will lead a group of six to eight campers on a weekend (or longer) winter hike into the Dolly Sods wilderness area near Davis, W.Va. About $45 a day per person for food, gear and guide. 731 Elden St., Suite 207, Herndon, Va. 22070, (703) 471-0171.